This invention relates to a strike-off beam and spreader plow assembly which can alternately be placed and supported spanning a subgrade to be paved behind a placer/spreader. More particularly, mounts are provided to removably mount the strike-off beam and spreader plow on either spanning side of the placer/spreader to permit the loading of concrete from either side of the placer/spreader. The mounts permit rapid transfer of the strike-off beam and spreader plow assembly to enable the placer/spreader to receive concrete from access roads on opposite sides of a subgrade being paved.
Slipform pavers are commonly utilized for paving reinforced and non-reinforced concrete roadways and airfield pavements. It is common practice for the concrete delivery trucks to back up on the subgrade and dump the contents of the truck on the subgrade in the path of a slipform paver and thereafter spread the placed concrete into the final profile of the specified concrete slab section. However, in some cases it is not possible for the trucks to drive on the subgrade of the roadway in the path of the slipform paver, and a separate access road must be employed alongside the road. In this case a placer/spreader can be utilized.
Access roads are required along the road subgrade when the subgrade in front of the slipform paver is not suitable or available for driving and dumping (such as when the subgrade is extremely porous, for example where superior drainage under the placed pavement is desired) or is too soft and thus not supportive enough for the concrete delivery trucks. Placer/spreaders are also utilized to receive and distribute concrete over the top of pre-placed dowel basket assemblies or continuous reinforcing bar reinforcement supported off and secured to the subgrade that would otherwise block the path of the concrete delivery trucks.
Placer/spreaders having roll in/roll out conveyors require occasional disassembly. Specifically, where the access road for concrete delivery is moved from one side of a paving path to an opposite side of the paving path, it is necessary to relocate the conveyor to the opposite side of the placer/spreader. In the prior art, this required removing the conveyor from its supporting frame, reversing the conveyor end for end, and reinstalling the conveyor to telescope into and out of the opposite side of the supporting frame.
In the mid-1960s, CMI Corporation (originally Construction Machinery Inc.) of Oklahoma City, Okla., manufactured a placer/spreader known as the PST 400 having the above-described construction with a roll in/roll out conveyor belt. Since then, another manufacturer copied this machine in its entirety. The machine included a main tractor frame with two side bolsters supporting an underlying concrete spreader auger with strike-off and an attached overlying power unit. The main tractor frame had an attaching rear bolster. Attached to the front of the main tractor frame was a conveyor supporting frame (conveyor module) which had an underlying roll in/roll out conveyor and attaching side bolsters. The entire assembly (main tractor frame and conveyor supporting frame) was supported on four bolsters with jacking columns and had crawler tracks at each corner of the entire assembly. Where the access road changed sides on the paving path, conveyor removal was required for relocation to the other side of the machine.
Additionally, this machine had superior function and productivity but was bulky, requiring multiple loads to be transported between job sites.
Specifically, three discrete loads require transportation. Further, both assembly and disassembly of the unit require a large crane assist. Regarding the loads, a first load includes the main tractor frame with the power unit and the underlying spreader auger assembly. A second load includes the conveyor supporting frame with the underlying roll in/roll out conveyor. A third and final load includes the disassembled front and rear bolsters, each with a jacking column and the supporting crawler track. Disassembly and assembly of the placer/spreader was and is very time-consuming, taking days to set up and tear down.
Moreover, the two discrete frames, each with two or more cross beams spanning the substrate, namely the conveyor support frame and tractor frame, required re-sectionalization when a width change of the placer/spreader is required, say to change the width from a standard 24-foot wide pavement to a 30-foot wide pavement. This too required a large crane assist and was very time-consuming, taking days to change the width.
This machine utilized spreader augers. Spreader augers utilized by the prior art are less than optimum. Typically, and because of the limits of the auger flighting and the mass of the auger, a central support bearing is required to support the auger from the main tractor frame. The supported auger includes opposed auger flights terminated at a central bearing. Further, such augers have a diameter in the range of up to three feet in order to be large enough to spread concrete rapidly. Finally, and assuming that more concrete is placed on one side of the auger support bearing than on the other side of the support bearing, redistributing concrete across the central support bearing of the spreader auger is problematic at best. Furthermore, spreader augers are dangerous and very costly to operate because of the auger fighting, and bearings wear out rapidly when conveying abrasive concrete.